A British-based group that backs the opposition says more than eight troops were slain at a checkpoint near Saraqeb, and labels it a "massacre."

BEIRUT — New video emerged Thursday that appeared to show Syrian rebels beating and kicking government soldiers captured at a checkpoint and then training their rifles on the huddled prisoners, executing at least eight.

Amnesty International issued a statement saying the "shocking" footage "depicts a potential war crime in progress."

The British-based Syrian Observatory for Human Rights, a pro-opposition group, labeled the incident a "massacre" and said more than eight soldiers had been executed at the checkpoint outside the town of Saraqeb in Idlib province.

The opposition group reported at least 157 killed Thursday across Syria, including at least 72 government soldiers and 16 rebel fighters. The numbers could not be independently confirmed.

There was no immediate response from the Syrian government.

Fierce fighting has been reported at government checkpoints in the Saraqeb area, about 25 miles south of the embattled city of Aleppo. Government forces are battling to keep open supply routes to troops fighting in Aleppo, which has been a battleground for more than three months.

Human rights groups have accused both government and rebel troops of carrying out extrajudicial executions in the Syrian conflict.

The video that surfaced Thursday was just the latest documenting apparent rebel executions of prisoners.

In late July, a disturbing amateur video was posted on YouTube showing Syrian rebels in Aleppo executing at least four half-naked, unarmed men — alleged to be pro-government militiamen — on the patio of what appeared to be a primary school.

The Free Syrian Army, a rebel umbrella group, later condemned those killings and said prisoners were to be treated in accord with international law.

But the group does not exercise central command over the scores of rebel bands that are fighting to overthrow the government of President Bashar Assad. Many Syrian rebel groups appear to act semiautonomously, responding only to commanders of their units.